Condensation happens when the air cannot change, and damp air then gets cold. In the big barn, there was good air exchange so no condensation. The more air-tight you make it the more you need to heat the space - with something like
Tubular Heaters under the machine. If you are going to heat the space then I can see value to fibreglass and hardboard but without adding heat I don't think the extra cost and effort is going to do much for you.
I'm not a builder, though
John
PS If I had that shed I would HAVE to make it look like Tracy Island, and "Pimp my Ride" to look like Thunderbird 2......... with a rotor coming out of the top, obviously